Hazardous or toxic chemicals, such as chlorine, sulfur dioxide and ammonia, are widely distributed in pressurized containers for use in water purification, sewage treatment, and a variety of other industrial and agricultural applications. Many of these chemicals are immediately toxic to humans, even in low concentrations. Accordingly, it is commonplace for the containers, valves, fittings and dispensing procedures for these chemicals to be strictly regulated by governmental regulatory bodies.
In accordance with such regulations, an operator who is properly equipped, trained, and certified usually connects and disconnects the pressurized storage containers used to store and dispense such chemicals. The containers are, however, routinely left unattended for extended periods of time while connected to process piping during filling and dispensing. Indeed, the chemicals in these containers are typically employed in applications requiring low dosage rates (for example, in ratios of the chemical to the treated fluid measured in a few parts per million). Thus, it may take days, weeks, or even months for the contents of such containers to be completely discharged. Consequently, it is generally impracticable for such containers to be continuously monitored by a live attendant during their use cycle.
In addition, if there is any leakage at the pressurized storage container, or at any other point in the facility where such toxic chemicals are used, the toxicity of the chemicals involved will often preclude the approach of an operator or technician without protective breathing apparatus and protective clothing.
For example, one conventional automatic valve actuation system for closing the filling/dispensing valve of a pressurized storage container includes a rotary valve actuator that can be controlled by a motor or that can be controlled manually. However, once a particular mode of operation, either manual or automatic, is selected by the operator, the alternative mode is effectively disabled. Disadvantageously, should the manual mode be selected and the system left unattended, emergency shutoff in the automatic mode would not be possible.
Another conventional automatic valve activation system, often used with bulk containers, employs a compressed air-driven valve actuator. Such systems generally are not suitable for use with application container valves. In addition, compressed air typically requires dehumidification and filtering to avoid freezing, corrosion, and particulate contamination, all of which can damage the system or cause it to malfunction. Such systems typically also require some mechanism for converting electrical signals to pneumatic signals, and vice-versa. Accordingly, compressed air systems are typically quite complex, bulky, and expensive.